Unable to get embedded subtitles to work

[Karl]

Hi !

I am trying to use the embedded subtitles of my media files for my Jellyfin clients as this is much more convenient than fetching external subtitles. However, in all cases I have encountered, the subtitles failed to display correctly. Different issues arose, depending on whether transcoding was required. 

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• When the server is not transcoding, the embedded subtitles do work, although with strange errors : with multiple subtitle tracks, the language displayed in the UI does not correspond to the real language of the subtitles that are ultimately displayed to the client. Despite my libraries being set to accept only text-based subtitles, Jellyfin continues to display image-based subtitles, yet the menu does not, thus causing a general mismatch between what is displayed to the user and what they had selected. For example, I have a media with both SRT and PGS subtitles ; when the first track in the menu is selected  — English (SRT) - SUBRIP —, the first track regardless of its formatting is displayed, i. e. the English PGS subtitles. Selecting the second track  — Arabic - SUBRIP — therefore causes the second of all tracks to be displayed, i. e. the English SRT subtitles, and so forth.
  

• When the server is transcoding, the embedded subtitles do not work at all, and none of them are displayed to the client. In the logs, I can see the following error : 
  Code:

  System.ArgumentException: Unsupported format: srt
  
  

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Regarding the second type of error, there is another post mentioning the same issue : on the Jellyfin forums ; based on the linked Github issue, I was able to determine that : (a) my Jellyfin does not appear to be corrupted, as neither deleting the subtitles folder nor reinstalling Jellyfin entirely did not solve the problem ; (b) the embedded subtitled are indeed in the correct format, as I was able to extract meaningful subtitles using Subtitle Edit, and reading the media through VLC with subtitles did work. I have the transcode subtitles on the fly option activated, and tried the Subtitle extract plugin in the hope that it might solve the issue, yet to no avail. I am therefore running out of hypotheses.

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Some useful informations about my setup :

Jellyfin : 10.10.7 via Docker ;
Hardware : Transcoding is done with Quick Sync on an i3-7100T ;
The test was conducted with Jellyfin Media Player 1.12.0 on Windows 10.

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Any help is appreciated, and thank you for developing such an awesome software !

[bitmap]

I would recommend using the subtitle extract plugin, which will extract text-based subs to SRT format and store them next to the media files. This means you don't have to fetch anything. When subtitles are embedded, they have to be extracted ANYWAY and may be stored in cache unless you're using the aforementioned functionality. In most cases it takes a few seconds, but they are extracted in their entirety before they display at all, which can cause a large delay.

You can also check standard behavior with subtitles, as I know many clients have a setting to not display subtitles or only display the selected language regardless of defaults. You may also consider learning to use ffmpeg or, even better, mkvmerge (MKVToolNix) to strip PGS subs if you don't want them present. I do this with all my 4K media, as PGS subs will cause transcoding and tonemapping, which is a suboptimal experience.